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Re: Laptops as servers?
From: Bennett Todd <bet () rahul net>
Date: Thu, 15 Jun 2000 09:47:25 -0400


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2000-06-15-01:07:44 Jerry Scharf:
One thing I know to watch for is periodic battery replacement. It
turns out that running a laptop with a battery in it with AC on
all the time will slowly erode the life of the battery.

That was definitely a major and severe problem at least a few years
back; when the state of the art laptop used an NiCd battery, and had
fairly dumb charging circuitry that easily overcharged --- and so
overheated, and hence damaged --- the batteries, leaving it plugged
in all the time killed it relatively quickly. People confused this
with the subtle "memory effect", which they'd never be able to
notice in laptop use.

But a modern laptop, with brilliant power management software
managing the health of a LiIon battery doesn't seem to suffer from
this problem nearly as badly. I've been using my Sony Vaio 505TX
for a year as my desktop computer; it's run pretty much a superset
of 9-5 M-F plugged in to wall power, and I still get a reasonable
battery run. And I'd still expect to use an external UPS with the
laptop servers; I'd just expect the laptop's battery to provide a
little extra coverage, and ability to ride over the switching. Plus
it wouldn't load the external UPS --- or the air conditioning --- as
hard.

I honestly think that laptop designers and manufacturers have
figured out people use their products as very compact desktop
computers. In fact, if I'm recalling correctly, Toshiba pulled out
an early commanding lead in the laptop industry in significant part
because they had a _huge_ local market of office users whose office
desks didn't have room for a US-styled "desktop" system.

The other is that the I/O on laptops sucks compared to PCI. For
things that aren't major traffic handlers (like your DNS and DHCP
examples) this is not a hit. Do any of the O/Ss out there get full
rate out of a 100bT PC card?

As you say, for some jobs it's not an issue. For sure it's easy to
get 10Mbps; I've done that for some time now with Linux through a
3C589. I haven't tried my 3C575 recently; a couple of Linuxes ago it
solidly hung the system. But CardBus _claims_ to support data rates
up to 132MB/sec.

Even if it's hard to tweak a CardBus 100BaseT to run at full speed
(I do not know), I honestly don't see that as being a major
limitation for the kinds of applications to which a laptop would be
otherwise suited. Maye it just reflects my youth and inexperience,
but I tend to start thinking about higher-speed interfaces (faster
than 10BaseT) about the same time I'm worrying about tuning a
striped or raided disk farm with multiple controllers. A laptop with
a single low-power (and hence low-rpm) IDE drive isn't competing at
the high-performance end of things.

There's actually a funny story there. I started using a laptop as a
desktop computer before CardBus came around, and so got accustomed
to the PCMCIA slot imposing a 4Mbps throttle on my ethernet. I
couldn't figure out why people bothered with 100BaseT cards at all.
I'd even confirmed the 4Mbps bottleneck with pathchar. Then I
started with a new laptop setup, and was seeing real observed
bandwidths up close to 10Mbps out of the likes of ftp, and was
puzzled for a while.

- -Bennett
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